Abstract
Acquired hemophilia A is a life-threatening immune-mediated hemorrhagic disorder that is most often found in individuals older than 50 who present with an unexplained activated partial thromboplastin time (aPTT) prolongation and clinically significant bleeding. The prolonged aPTT associated with acquired hemophilia A reflects factor VIII activity deficiency due to neutralizing or clearing autoantibodies. Deep venous thrombosis, in contrast, is a veno-occlusive disorder associated with several distinct hypercoagulable states that can result in significant morbidity and mortality due to pulmonary embolism, thrombus extension, and the post-thrombotic syndrome. A prolonged a PYI in the setting of thrombosis may reflect the presence of a lupus anticoagulant. In the absence of accurate diagnosis and the immediate institution of specific therapy, both disorders can be fatal. Three cases of acquired factor VIII inhibitors that included a prolonged aPTT, bleeding, and duplex ultrasound evidence of deep venous thrombosis are presented. The diagnostic and therapeutic challenges posed by these cases as well as a proposed mechanism by which pathologic thrombosis can develop in a patient with a life-threatening bleeding disorder are discussed.